Magnetic disks for storage of data signals in computer systems are widely used throughout the computer industry. The storage disks, typically made of aluminum substrates, are coated with a thin layer of material which is capable of storing data in the form of magnetic flux. One method of coating the storage disks with the magnetic material is to electroplate them.
The thin layer of magnetic material must be evenly distributed over the surface of the storage disk. Thus there must be uniform current distribution over the surface of the disk during electroplating. One arrangement used in electroplating the storage disks makes use of an electrically conductive carrier plate with a disk-sized cavity in the center. The storage disk substrate is inserted into the carrier plate cavity and a smaller conductive plate is inserted into the central hub aperture of the disk. The result is a composite plate which is electrically continuous.
The composite plate is inserted into a plating tank containing sufficient electrolytic solution to envelop the plate. An electrical current is then applied to the composite plate to electroplate the storage disk. The plating tank, which is only slightly larger than the composite plate, inhibits stray currents in the electrolytic solution, thus promoting even plating, as does the large, continuous surface provided by the carrier plate and the central conductive plate. After the storage disk is coated, the composite plate is removed from the plating tank and rinsed to remove the plating chemicals (commonly referred to as "chemical drag-out") that have not drained therefrom, and the magnetic disk is removed from the carrier plate. The rinse water is thereafter treated as chemical waste.
The disadvantages of this electroplating technique are: (i) the excessive disk handling required to insert the storage disks in the carrier plate cavity, sometimes resulting in physical damage to the disks; (ii) the large quantities of chemical drag-out removed from the plating tank with the composite plate, resulting in a large amount of chemical waste to be treated; (iii) the electroplating of the entire composite plate, requiring frequent replacement of the carrier plate; and (iv) the inefficiency of electroplating only one disk per plating tank at any time given.